Calcined layered double hydroxides as a "biomolecular vessel" for bromelain: Immobilization, storage and release

Calcined layered double hydroxide (LDO) has been used as the novel biomolecular vessel for the immobilization, storage as well as release of bromelain. The immobilization is attributed to physical adsorption without affecting the structure of LDO, and the optimum initial amount of bromelain was 20 ml of 4 mg/ml for 1 g LDO and the immobilized enzyme activity express was 33.4% at pH 6.5. The adsorption isotherm of bromelain/LDO can be well described with the Langmuir model with a R-2 of 0.9946, a maximum adsorption amount of 157 mg/g and the Langmuir adsorption equilibrium constant of 0.07 ml/mg. Significant improvements have been found in the stability of immobilized bromelain upon heat treatment (increase in residual activity and denaturation temperature) as well as storage time compared with those of free bromelain. In addition, the release maximum of bromelain reached to 70% and the residual activity maintained 81% in water solution at pH 7. (c) 2007 Elsevier B.V. All rights reserved.